Human Skin - Nude Mouse Model. We have established a model for long-term cultivation of adult human skin on the nude athymic mouse. Psoriatic skin can be grown for periods of several months and retain essential features of psoriasis. Epidermal kinetic studies confirm a hyperproliferative state in these grafts. Recombinant studies of normal and psoriatic epidermis and dermis are underway to determine the site of the pathologic defect in the disease. Studies are also underway utilizing the human skin-nude mouse system to study conservation of regional epidermal specificities and the effect of non-dermal connective tissue on epidermal maintenance. Formation and Function of Structures at the Epidermal-Dermal Junction and Diseased Human Skin. Studies are underway to selectively isolate components at the epidermal-dermal junction particularly basal lamina and anchoring fibrils. Clinical, genetic and ultrastrucutral features of patients with various types of epidermolysis bullosa are being studied to define and classify this confusing group of diseases. The effect of human skin collagenase structures of the epidermal-dermal junction is also under study.